A variety of functions, useful in micro-fluid and opto-fluid systems, such as the adaptation of the liquid meniscus form, the spatial geometric modulation or “patterning”, the shifting and drop formation [1-5-19], may be performed by different approaches, for example the “electro-wetting” (EW) or the thermo-capillary [2-20-21].
The traditional microfluidic systems are essentially based on hydrodynamic forces whereas the approaches assisted by electric field became more and more popular only recently, due to their advanced flexibility and their additional functionality [22-23]. The formation of micro- or nano-liter drops caused by electric field is useful in electro-spray mass spectroscopy, injkjet printing, biomolecular manipulation [16] that furnishes a so-called “on demand” distribution of material [7-15].
The solutions obtained with the standard electro-dynamic approach (EHD) are orders of magnitude better than those obtained with the thermal inkjet or piezo-electric [24] printers, and thus meet the growing request in the field of nano-technology of more sophisticated lithographic methods that are able to realize more fine and complex patternings. These EHD printing methods may also furnish the desired flexibility in the direct patterning of fragile biologic organic materials that are incompatible with the method of conventional patterning, such as the photo-lithography.
Nevertheless, in all of the mentioned methods, special nano-nozzles, electrodes, and circuits have to be designed and realized for each application. In addition, the EHD method requires the application of high voltages (e.g. in the “e-jet printing”), usually between the nozzle and the distribution plate, so as to allow the flow of fluid and its distribution on the substrate under examination.
Therefore, photo-lithographic methods are not easily used for such materials and, in the current situation, methods are not available that are characterized by high flexibility, simplicity and low cost, so as to permit easy change in the type of structure to be realized.
Recently, a new concept known as electrowetting has been developed, in which the manipulation of the liquid is achieved by a configuration in polar dielectric crystals, without electrodes. The functionalisation (i.e., in general, the adaptation of the crystal to activate a property) of a lithium niobate (LN) crystal is obtained by the micro-engineering of the ferroelectric domains [25] and the exploitation of the piro-electric effect. The modelling of the wettability, the formation of the liquid adaptable micro-lens matrix, and the auto-assembly of lithography have been demonstrated by this approach [26-27-28].
The first of the three previous mentioned works demonstrates the creation of a group of little drops spatially arranged on a surface starting from a liquid film. These drops function as a lens.
The second work demonstrates the use of such drops for non-optical purposes, for example for chemical and biological experimentation at nano-metric levels.
The third work demonstrates the mentioned creation of drops starting, this time, from a liquid polymer by means of a thermal stimulus. This thermal stimulus simultaneously provides for the “linking” of the same polymer, impressing a regular geometric configuration (“pattern”) to the polymer, and thus a lithographic method is obtained, in such a way.
It is the object of the present invention is to provide a method for the distribution of pico- or nanodrops of a material on a dielectric substrate, that solves the problems and overcomes the drawbacks of the prior art.
An additional specific object of the present invention is an apparatus that uses the method object of the invention.
An additional specific object of the present invention is the use of the apparatus, object of the invention, for printing.